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In Reply to: Calling "Imola Red M"... need 4x4 advice please + posted by Big-M on February 03, 2002 at 22:07:34:
1. Good recovery points. This is one of the most basic things but people forget it. What this means is that when you get stuck you need a way to get unstuck. I don't care what you drive you WILL get stuck at some point. I've seen a Hummer high centered (picture a mound of dirt under the driver door and all 4 wheels in the air this is poor break over angle) and had to get pulled out by a little Jeep YJ (Wrangler - less ground clearance but better break over angle due to short wheel base). I've also had to push with my bumper (on my Land Rover) against a front bumper of a Jeep Grand Cherokee to get him out of a hole because he had no recovery points. This could have done more damage to his vehicle than just paint damage. Recovery points should include rings up front and rear. A Class III hitch receiver in the rear can be used as a recovery point. Tow down loops are NOT recovery points and can and will come off in a recovery situation. You don't need a winch but you will need another vehicle for this to work. Use the buddy system.
2. This can be part of item 1. But vehicles with a box frame are much better than uni-body vehicles. You have a good place to anchor recovery points on a box frame. No matter how good a uni-body is like the X5 it will not hold up off road for long. Just ask any Jeeper about the JGC.
3. Live (solid) axles will offer more articulation than independent suspension (IFS/IRS). Live axles do contribute to the unsprung weight that IFS/IRS doesn't but this weight helps push down the other wheel. I'll try to explain. If you try to cross a ditch you should do it at almost a 45 degree angle (or your vehicles nose might hit the other side of the ditch). Lets say your front passenger wheel enters the ditch first. As you progress into the ditch with a solid axle vehicle (like Land Rover Defender or Discovery or Jeep Wrangler TJ/YJ) the weight of the axle will force that front passenger wheel to drop into the ditch. As you cross the right front wheel will begin to climb out of the ditch as your driver wheel will drop into it. With IFS like on a X5 one wheel will tend to float since there is no weight to push the wheel down. So what you say? After all the Hummer has independent suspension. Well... two things... First one way to get traction is to keep all wheels on the ground. One wheel in the air will cause power on the front to go to the front wheel with less traction. ETC will help overcome this and my guess is that Davids pictures of his X5 crossing a ditch made it due to the ETC putting the brake on the free wheel and thus forcing power to the wheel with traction. There is a point that the ETC will just not work. A wheel in the air isn't going to help you with forward momentum. Also having a wheel in the air changes the dynamics and you become more prone to tip in extreme situations. There is a video somewhere of a guy who took his hummer on a RTI ramp (RTI ramps test articulation) and the guy just rolled his vehicle because his front wheel was off the ground. The Hummer gets around the traction issue with 3 Differential lockers that keep all 4 wheels moving that is more effective than ETC but you can't turn the vehicle well (if at all) when all differentials are locked. To see some pictures of Rovers on a RTI ramp to get an idea of what I'm talking about check out http://www.bb4wa.com/events/adamwaypix.htm Also look at axles of my vehicle bellow...
3. Transfer case. You need a low range gearing for use off road. There are times when even 1st gear on an engine like the 4.4i won't give you enough torque or crawling speed that a reduced gear ratio will give you. Sand is another place where you want your wheels spinning slowly or you'll find yourself axle deep. Contrary to what you see on TV you don't want to go fast and spin your wheels when off road. Unless you want to be the next winner of the Darwin Awards =)
4. Suspension. This isn't that important but will help with articulation. I already mentioned the issue with the axle and how that helps. But the suspension will help too. Coil springs will give you more articulation that leaf springs. Many sales people will tell you that the solid/live axles are what give the truck like ride. They're only 20% right. SUV's like the Durango with IFS and leaf springs ride much worse and "Truck" like than my solid axle coil sprung Land Rover. Jeep has caught on to what Land Rover has known for decades. The Jeep Wrangler TJ and Jeep Grand Cherokee both have solid axles and coil sprung (aka Quadra Coil).
There are more things that go into it like approach, break over and departure angles but I won't get into that. The biggest weakness of the X5 off road is the lack of a low range. If you want to be able to handle light off road the X5 should be okay. The Sport tires area a weakness too but if you want to drive on a dirt road or muddy field the X5 should be fine. I drive an X5, a 540i/6 and Land Rover Discovery II. Until recently I also drove an M Roadster. The Discovery is modified to handle some nasty stuff but even that won't do as well as a stock Defender 90. Right now if you want a good off road vehicle you have two choices. They are the Jeep TJ like the new Rubicon or the MB G-Class. Or get a used Land Rover and that way you don't have to worry about the depreciation. BTW - you can sell a 1997 Defender 90 for more that you paid for it if you sold it today. =)
If there is anything you would like me to try and explain more please let me know. If I missed any definitions also let me know. If you ever want a vacation and learn some offroading I would recommend www.bb4wa.com. Bill is very good and will teach you in one of his Land Rovers in the South west. Or If you're in the DC metro area I would be glad to take you out on some area trails.
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